The invention relates to insecticide-impregnated nets made of textile fibers, which nets have a small mesh size, and their use for the protection against pests.
Insect protection nets are known in principle. For example, they are used as windows in order to keep all sorts of insects as well as larger animals such as birds or rodents out of the house. Another example which may be mentioned is the use of mosquito nets. Insect protection nets are furthermore used for protecting plants, plant parts, fruits or non-living materials from pests, for example by wrapping the plants or materials to be protected in them, or by using the nets as windows in greenhouses or for the construction of greenhouses.
Insect protection nets are commercially available with different mesh sizes. Typical mosquito nets made of polyester have meshes with a size of approximately 2 mm×2 mm; commercially available mosquito nets made of polyethylene monofilament frequently have hexagonal meshes, the distances between the parallel sides being 2.5 mm.
However, small insects such as, for example, thrips, whiteflies or sand flies, are still capable of passing through nets with such a mesh size. In “Screen hole size and barriers for exclusion of insect pests of glasshouse crops” J. Entomol. Sc. 26: 169-177 (1991), Bethke et al. specify a “critical insect diameter” of approximately 0.2 to approximately 0.6 mm for a variety of relatively small insects. Nets through which even the above insects should no longer be able to pass must, therefore, have considerably smaller mesh sizes than customary mosquito nets. Commercially available nets for protection against such insects have mesh sizes of less than 1 mm×1 mm down to 0.15 mm×0.15 mm.
However, it is a disadvantage that the permeability of the net to air, water vapor and light also decreases with decreasing mesh size. Thus, the permeability to air of very close-meshed nets may frequently be reduced by approximately 50% in comparison with wide-meshed nets. This decrease in permeability is highly undesirable for many applications of the nets, in particular when used as window materials for greenhouses; rather, a sufficient air exchange and the diffusion of water vapor should be possible, and, also, the light intensity must not be unduly reduced.
It is furthermore known to impregnate insect protection nets, in particular mosquito nets, with insecticides.
WO 2003/034823 discloses a formulation for impregnating mosquito nets and nets impregnated therewith, which formulation comprises at least one insecticide, a copolymeric binder and at least one dispersant.
WO 2005/064072 discloses a formulation for impregnating mosquito nets and nets impregnated therewith, which formulation comprises at least one insecticide or other active ingredient and at least one binder. The binder may take the form of a polyacrylate which comprises, as monomers, at least n-butyl acrylate, an acrylate which differs therefrom, and at least one hydroxyalkylacrylamide.
EP 1 411 764 B1 discloses fences for preventing the penetration of low-flying insects into certain zones in the open, which fences comprise insecticide-impregnated nets.
WO 2007/144401 discloses a method for protecting tobacco, where the tobacco is covered with an insecticide-impregnated material, for example an insecticide-impregnated net. The examples disclose nets with square meshes 2 mm×2 mm or 1 mm×1 mm in size.
WO 2008/52913 discloses a method of protecting useful plants, where the plants are covered with a pesticide-impregnated net which is permeable to light, air and water.
JP 2270803 A discloses a net for protection against insects, the threads of which are obtained by melting together an ethylene/vinyl acetate copolymer and the active ingredient empenthrin and optional further active ingredients. The threads may have a diameter of from 0.2 to 1 mm, and the mesh size is 2 to 4 mm.
JP 2001-292688 A discloses an insect protection net for fitting into windows of dwellings, offices and greenhouses, which insect protection net is made of polyolefin fibers and is coated with an acrylic resin. The mesh density is 20×20 threads per direction and inch; this corresponds to a mesh size of approx. 1.5 mm2. However, the net is not impregnated with insecticides.
WO 2008/004711 discloses a net for controlling insects, the fibers of which net have a thermoplastic polymer and an active ingredient with a vapor pressure <1*10−6 mm Hg at 25° C., and the net having essentially identical meshes with an area of in each case 2 mm2 up to 36 mm2.